Conventionally, there has been developed a technique for detecting a subject around a vehicle.
For example, Patent Document 1 discloses a pedestrian dash prediction system. The pedestrian dash prediction system acquires a time-series change in the location and moving speed of a pedestrian present ahead of a host vehicle and surrounding information, compares the acquired time-series change in the location and moving speed with the pattern of a time-series change in the location and moving speed of a pedestrian at the time when the pedestrian runs out into a roadway and also compares the acquired surrounding information with pre-obtained surrounding information at the time when a pedestrian runs out into a roadway, and then predicts whether the pedestrian runs out into a roadway on which the host vehicle is traveling.
Patent Document 2 discloses a pedestrian recognition system. The pedestrian recognition system generates an edge image from image data that are input from an external sensor, detects an opening degree W between the right and left legs of a pedestrian candidate and also estimates the head of the pedestrian candidate, estimates the height H of the pedestrian candidate on the basis of the location of the head, and determines whether the ratio (W/H) of the opening degree W between the legs to the height H is larger than or equal to a predetermined value a on the basis of the height H of the pedestrian candidate and the opening degree W between the legs of the pedestrian candidate. Thus, the pedestrian recognition system determines whether there is a possibility that the pedestrian candidate crosses the path of the host vehicle.
Patent Document 3 discloses a vehicle exterior monitoring system. The vehicle exterior monitoring system obtains a location at which a three-dimensional object is present and its distance by generating a histogram for each of sections into which a distance image is divided by predetermined intervals, integrates the sections of which the distance is close as a group, splits each group at a portion at which an arrangement direction of data significantly changes, then re-combines the groups on the basis of mutual positional relationships of the groups, recognizes a single three-dimensional object as a combination of an object and a side wall, and calculates parameters, such as the location of the three-dimensional object and the longitudinal and lateral moving speeds of the three-dimensional object, by calculating the location of a corner point of the three-dimensional object. Thus, the vehicle exterior monitoring system detects the location and behavior of a vehicle diagonally ahead.